1 -> I 
2 -> II 
3 -> III 
4 -> IV 
5 -> V 
6 -> VI 
7 -> VII 
8 -> VIII 
9 -> IX 
10 -> X 
11 -> XI 
12 -> XII 
13 -> XIII 
14 -> XIV 
15 -> XV 
16 -> XVI 
17 -> XVII 
18 -> XVIII 
19 -> XIX 
20 -> XX 
25 -> XXV 
30 -> XXX 
40 -> XL 
50 -> L 
60 -> LX 
69 -> LXIX 
70 -> LXX 
80 -> LXXX 
90 -> XC 
99 -> XCIX 
100 -> C 
200 -> CC 
300 -> CCC 
400 -> CD 
500 -> D 
600 -> DC 
666 -> DCLXVI 
700 -> DCC 
800 -> DCCC 
900 -> CM 
1000 -> M 
1009 -> MIX 
1444 -> MCDXLIV 
1666 -> MDCLXVI 
1945 -> MCMXLV 
1997 -> MCMXCVII 
1999 -> MCMXCIX 
2000 -> MM 
2008 -> MMVIII 
2010 -> MMX 
2011 -> MMXI 
2500 -> MMD 
3000 -> MMM 
3999 -> MMMCMXCIX